NHSA Module 3 Practice Test

When a crash happens, your body wants to keep moving at the car’s speed because of inertia. A seat belt provides a restraining force that slows your body along with the car, keeping you in the seat and spreading the stopping forces across stronger parts of your body. This reduces the chance of hitting interior surfaces or being ejected and also helps airbags cushion you by keeping you in the proper position.

The other ideas aren’t accurate: seat belts aren’t optional and do affect you during a crash; they don’t slow the car’s momentum through seat friction—the belt acts on you, while the car’s deceleration comes from the crash itself; and belts don’t deploy after airbags—the belt is worn to restrain you immediately, while airbags deploy based on rapid deceleration.